Plasticized compositions



Patented Nov. 27, 1945 UNITED STATES PATENT OFFICE PLASTICIZED COMPOSITIONS Russell '1. Dean, Stamford, Conn, asslgnor to American Cyanamid Company, New York, N. Y-, a corporation of Maine I No Drawing. Application September 26, 1942,

1 Serial No. 459,822

8 Claims. (01. 260-36) Thisinvention relatesto the softening or plasticizing of natural and synthetic rubber-like compositions suitable for various applications.

In the use of various available compounds i'or the production of synthetic rubber-like materials, it has been found necessary to employ various plasticizers and softening agents. Many'of these plasticizers are costly materials and are diflicult to incorporate by milling into'the compositions. In addition. some of these plasticizers require a more or less extended aging period for the development of maximum plasticity. Furthermore, certain of the plasticizers which are used for assisting inthe milling operations must be removed before the flnal curing of the rubber composition.

It is an object of the present invention to pro- 'vide a new class of plasticizers for rubbery materials, which' plasticizers are effective elasticators while, at the same time, they avoid the principal objections to the plasticizers previously available.

These and other objects are attained by using as plasticizers for the natural and synthetic rubbers p-alkoxy and fl-aryloxy propionic acid esters having the following structural formula:

R-OCHzCHzCOOR' Butyl e-n-hexoxy propionate Butyl S-cyclohexoxy propionate Buiyl ,B-benzyloxy propionate Butvl B-tetrahydroiurfuryloxy propionate Butyl s-benzyloxyetho'xy propionate Butyl fl-ethoxyethoxyethoxy propionate Butyl fl-butoxyethoxyethoxy propionate Butyl s-phenoxy propionate I V Butyl fl-o-methylphenoxy propionate Butyl B-m-methylphenoxy propionate Butyl B-p-methylphenoxy propionate Butyl p-o-chlorophenoxy propionate Butyl e-p-chlorophenoxy propionate Butyl p-o-ter-amylphenoxy propionate Butyl p-tolyloxy propionate 2-Ethyl hexyl B-phenoxy propionate 2-Butoxyethyl B-Z-butoxyethoxy propionate n-Hexylp-rhenoxy propionate.

These and similar compounds falling .within the scope of the present invention may be made by any suitable method. It has been found that a simple method for their preparation comprises reaction of thecorresponding nitrile and alcohol in the presence of a molecular proportion of sulfuric acid, the esteriflcation reaction being carried out at about -120' C. in accordance with known procedures. The desired nitriles are conveniently prepared by the condensation of acrylonitrile with the desired alcohol or phenol.

The plasticizers of the present invention are, as indicated, especially effective when used in the production of rubber-like compositions. Such synthetic rubber-like compositions include those prepared from vinyl chloride polymers, chloroprene polymers, polymerized diolefins and copolymers of dioleflns and olefins, isobutene polymers, organic polysulfldes and the various copolymer types of synthetic rubbers including polyacrylyl or polyvinyl compounds such as butadiene 1.3 and acrylonitrile copolymers or butadiene 1,3 and styrene copolymers, and the like. The incorporation of the plasticizer with the rubber-like material may be carried out in accordance with the usual practice, during the milling or breaking-down period, e. g., on the mill rolls. The amount of the softening agent used may be varied widely and in general will be governed by the particular softening agent selected, the degree of toughness of the synthetic rubber-like mass, the extent to which softening of the latter is desired,.and the other properties which it is desired to impart to the rubber-like composition. In generahthe amount may be from about 5% or less to about 50% based on the weight of the synthetic rubber-likematerial.

As illustrative of suitable methods for incorporating the plasticizers of the present invention into the various compositions, the following examples are given without restricting the invention thereto.

EXAMPLE 1 One hundred parts by volume of polyvinyl chloride were mixed in a suitable container with 89 parts by volume of the selected plasticizer. This mixture was gradually fed onto a 6" x 12" open mill, the rolls of which were set tightly together and which were maintained at a temperature of about C. The mixture, after having been passed once through the rolls, was in the form of a flaky product and was returned to the tightly-set rolls until a continuous sheet began tovform. The period of time required to form this sheet was noted as the sheeting time. The milling 'of the product was continued with gradual opening of the rolls to allow the mixture 9. to build up a rolling bank of about 4" diameter.

Without additional adjustment of the rolls, the milling was continued until a reasonably translowing table in which, for comparative purposes, I

dibutyl phthalate is set forth as a standard.

Table 1 Actual Mllling 22; Brittle point time percent Butyl fl-cyelobexory pro- C'.

onate 6% 18. 8 28. 0 60 Butyl B-tetrahydrolurluryloxy propionate 6% 24.3 33.0 60 Butyl fi-benzyloxyothoxy propimmtc 6% 23.4 34.3 Below -46 Butyl B-ethoxyethoxyethoxy propionate 7% 34. 6 32. 0 Below 57 Butyl fl-butoxyethoxyetbory propionate 8% 22. 9 32. Below 57 Butyl fl-phenoxy propionate. 6% 23. 5 34. 2 Below 40 Butyl fl-o-metbylphenoxy propionate 6% 2i. 9 33. 2 55 Butyl B-mmetbylpbenoxy propionate 6% 25. 2 35. 4 60 Butyl B-p-metbylpbenoxy pro iouate 6% 25.0 34.7 --55 Buty fi-p-cbloropbenoxy profiionate 6% 25. 8 36. 5 -50 Buty fi-o-ter-amylpbenoxy prorionato l0 2i. 6 28. 6 50 Buty fl-tolyloxy propionate. 634 23.8 33.2 55 2-etbyl hexyl B-pbenoxy proliiiomqeb -il 8 22.0 31.4 Below -57 nexy -p enory proplonate 6% 20. 3 35. 6 65 Dlbntyl phthalate 6% 23. l 31. 7 45 solvent loss and/or lower heat loss than dlbutyl phthalate, they are superior for many uses or applications. So far as the other physical properties such as elongation, tensile strength and the like, are concerned, the plasticizers of the present invention give substantially the same or superior results in comparison with those obtained with dibutyl phthalate.

Exnutn2 Hycar 100 Plasticizer }prevlmjlsly mixed 50 Channel black 50 Zinc c 5 Sulfur 1.5 Stearic acid 1 Phenyl-p-naphthylamine 1 Benzothiazyl disulfide .95 Zinc chlorideDOTG reaction product"- .20

After formulation, each batch was allowed to cool overnight and was then remilled and cooled for about 4 hours. These products were then cured in the form of sheets by heating for 30 minutes at a temperature of 153 C. The results obtained are contained in the following table.

Table 2 Apparent lncorpo- Impact ration :3 reslli- 2: Brittle point tlmc percent enee "C. Butyl fl-benzyloxy ropionate... 14 0.2 64 23.0 Below -40 Butyl B'ethoxyct oxyetboxy pro lonate 16 0.9 04 22.9 Below 46 Buty B-butoxyetboxyetboxy proplonate 20 9. 6 62 25. 7 Below -46 Butyl B-pbenoxy ropionste. 15 8. 1 67 22. 8 Below --46 2ethyl hexyl fi-p cnoxy proplonate 13 4. 2 25. 2 Below -46 2-buioxyethyi B-Z-butoxyeihoxy Prupionate 24% 8. 5 24.2 Below 46 D butyl phthalste 16 3.4 47 26.3 45

plasticizer for polyvinyl chloride, those plasticizers which show characteristics at least as good or superior to dibutyl phthalate are valuable for this urpose. where the plasticizers show lower The apparent solvent loss represents-the percentage change in weight of a sample after soak-' ing for 48 hours in hexane and wiping the sample.

The heat loss represents the percentage loss in weight after heating for 48 hours in an oven at 150 C. v

The brittle point is the temperature at which the sample broke on being bent through an angle of The impact resilience is the reading indicated 7 by the Shore scleroscope, the higher there'ading the more resilient the stock, thus indicating that the plasticizer is a better elasticator.

The plasticizers giving lower solvent loss, lower heat loss, lower brittle points and/or higher reexample the tetrahydrofurfuryl radical.

silience than dibutyl phthalate are generally more desirable plasticizers, especially for such purposes as require superior properties in these respects. The other physical characteristics of the cured stock, such as plasticity (Y values). tensile strength, elongation, etc. are generally as good as, or superior to, the same properties obtained when dibutyl phthalate is used.

Mixtures of a natural rubber with one or more of the synthetic rubber-like materials of the kind referred to may also be obtained in a softened condition by the use of one or more of the plasticizers of the present invention. Furthermore, natural rubbers may, themselves, be plasticized by milling them with a relatively small amount of one of the present plasticizers, about 1-10% on the weight of the rubber being sufficient in most cases.

Where it is desired to obtain mixtures of two or more of the synthetic rubber-like materials described, either with each other or with a natural rubber, such mixtures are preferably prepared by first milling the tougher of the materials with one of the plasticizing agents so as to bring the same to a condition of softness approximating that of the softer component or components. Additional plasticizers may be added as milling is continued.

The quantity of plasticizers may be varied as well as the temperature and the length of time of mixing. In general, these interrelated factors will be governed by the efficienc of the plasticizer selected as well as by the nature of the natural or synthetic rubber-like materials. The rate of incorporation of the plasticizers may be increased by raising the mixing temperature although it would obviously be undesirable to use such temperature as would have harmful effects on the ingredients of the mixture. Likewise, the size of the batches mixed will affect the mixing time. The plasticized rubber-like compositions prepared in accordance with the present invention may be used wherever compositions of similar character are now employed. Thus, these compositions may be used in the waterproofing of fabrics as well as in the production of calendered,

extruded or molded articles. The compositions may include various fillers, pigments, dyes, or the like.

In the plasticizers of the present invention the alkyl group represented by R in the generic formula may also be a heterocyclic group, for While the alkyl groups may be those of the lower boiling alcohols such as methyl and ethyl, such esters may be too volatile for some purposes. For the purpose of producing best plasticizers, it is generally preferable that the alkyl groups contain carbon in which R is a member of the group consisting of the alkyl and alkoxyalkyl radicals and R is a member of the group consisting of the alkyl, alkoxyalkyl, cycloalkyl, aryl, aralkyl, aralkoxyalkyl and tetrahydrofurfuryl radicals.

2. The processof plasticizing and softening butadiene 1 iii-acrylonitrile copolymer synthetic rubber-like materials which comprises admixing with such materials butyl B-phenoxy propionate.

3. The process of plasticizing and softening .butadiene 1,3-acrylonitrile copolymer synthetic rubber-like materials which comprises admixing with such materials butyl p-cyclohexoxy pro pionate. I

4. The process of plasticizing and softening butadiene 1,3-acrylonitrile copolymer syntheticrubber-like materials which comprises admixing ,with such materials n-hexyl ,B-phenoxy propionate.

5. A composition comprising butadiene 1,3 acrylonitrile copolymer synthetic rubber-like materials, plasticized with a p-substituted oxypropionic acid ester having the following structural formula:

R-OCHzCI-IzCOOR' in which R. is a member of the grou consisting of the alkyl and alkoxyalkyl radicals and R is a member of the group consisting of the alkyl, alkoxyalkyl, cycloalkyl, aryl, aralkyl, aralkoxyalkyl and tetrahydrofurfuryl radicals.

6. A composition comprising butadiene 1,3- acrylonitrile copolymer synthetic rubber-like materials, plasticized with butyl p-phenoxy propionate. I

7. A composition comprising butadiene 1,3- acrylonitrile copolymer synthetic rubber-like materials, plasticized with butyl p-cyclohexoxy propionate.

8. A composition comprising butadiene 1,3- acrylonitrile copolymer synthetic rubber-like materials, plasticized with n-hexyl c-phenoxy propionate.

RUSSELL T. DEAN. 

